Wellbore measuring instruments, known as measurement-while-drilling and logging-while-drilling instruments, are used in connection with drilling a wellbore through a geotechnical or multiple geotechnical formations. Such wellbore measuring instruments are coupled to a pipe that is used to move a drill bit through the formation to lengthen (drill) the wellbore. These instruments include sensors that measure parameters related to a wellbore trajectory, for example, and/or properties of the formations outside the wellbore. Instruments may typically include a communication device that converts selected measurements made by the sensors into signals that are transmitted to the surface by modulating the flow of drilling fluid in the pipe. The drilling fluid is used for, among other purposes, to cool and lubricate the drill bit and to lift drill cuttings to the surface. The drilling fluid is pumped under pressure from the surface through an interior opening in the pipe string. Communication systems modulate the flow of the fluid so that a signal is detectable at the surface which corresponds to the signal transmitted by the instrument in the wellbore. Typically, the signal is detected using one or more pressure transducers in hydraulic communication with the interior of the fluid system on the discharge side of the pump or the entry point therefrom to the interior of the drill string. A representative example of a mud flow modulation telemetry system and signal detection devices associated therewith are shown in U.S. Pat. No. 5,955,966 issued to Jeffryes et al. and assigned to the assignee of the present disclosure.
There is a need for improved techniques to detect fluid flow modulation telemetry signals from instruments in a wellbore.